Conventionally, various conveying devices for a workpiece have been proposed.
As one conveying device, for example, there is known a belt conveyor which conveys an object to be conveyed such as a workpiece by placing the object to be conveyed on an endless belt (annular belt) looped around a drive rotating body and a driven rotating body.
Further, for example, there is known a conveyor (conveying device) as illustrated in FIG. 9.
This conveyor is a so-called slat conveyor (slat conveyer). As illustrated in FIG. 9, on an outer periphery of an endless chain (annular chain) looped around a drive-side rotating body, such as a drive-side sprocket rotationally driven by an electric motor and the like, and a driven-side rotating body, such as a driven-side sprocket, a plurality of slats (plate-like members made of metal, resin, wood, etc.) each having a relatively narrow width are mounted so that a longitudinal direction of each slat is substantially orthogonal to a traveling direction of the endless chain (annular chain). The object to be conveyed such as a workpiece is placed on the slats to be conveyed.
In such a conveying device, when the size of the product to be conveyed (object to be conveyed such as a workpiece) is changed along with a change of the workpiece or the like, the conveyor width may be desired to be changed in accordance therewith in some cases.
In such cases, a plurality of conveyors are used, and the width-direction positions of the respective conveyors are changed, thereby enabling adjustment to the size of the object to be conveyed.
As an example of a device of this type, there is known a conveyor described in Japanese Utility Model Application Laid-Open No. S60-36918 (hereinafter referred to as Patent Literature 1).
The conveyor described in Patent Literature 1 is configured so that, as illustrated in FIG. 10, an interval between two belts 9 arranged in parallel to each other can be changed.
In the case of a conveyor of the type as described in Patent Literature 1, the sum of the widths of the plurality of belts (or slats) is the minimum width of the conveyor, and when it is desired that the width of the conveyor be increased to be larger than the minimum width, a parallel gap (parallel groove) extending along the longitudinal direction (conveying direction) of the conveyor is generated between one belt (or slat) and another belt (or slat) adjacent thereto.
Therefore, for example, the whole or part of one object to be conveyed may fall through the above-mentioned parallel gap to cause an unstable conveying state. Thus, the object to be conveyed may not be smoothly conveyed.
In order to avoid falling of the object to be conveyed through the parallel gap extending in the longitudinal direction as described above, in the conveyor described in Japanese Utility Model Application Laid-Open No. S55-101809 (hereinafter referred to as Patent Literature 2), as illustrated in FIG. 11, movable covers 4 and 5 and a fixed cover 6 are provided between two conveyor belts 1 and 2, and when the interval between the conveyor belts 1 and 2 is increased, the movable cover 4 integrated with the conveyor belt 1 and the movable cover 5 integrated with the conveyor belt 2 are moved on the fixed cover 6, thereby covering the parallel gap between the conveyor belts.
However, in the conveyor described in Patent Literature 2, when the width between the two conveyor belts 1 and 2 is desired to be decreased, the movable cover 4 and the movable cover 5 may interfere with each other, which hinders sufficient decrease of the width between the conveyor belts. Therefore, in an actual situation, a small object to be conveyed or the like cannot be satisfactorily conveyed.
Further, there is a relative speed difference between the conveying surfaces of the respective two conveyor belts 1 and 2 which move at a predetermined speed in the conveying direction, and the surfaces of the respective movable covers 4 and 5 which are fixed in the conveying direction. Therefore, when a part of the object to be conveyed supported by the conveying surfaces of the respective conveyor belts 1 and 2 is brought into contact with the surfaces of the movable covers 4 and 5, the object to be conveyed becomes unstable. Therefore, in an actual situation, the object to be conveyed cannot be smoothly conveyed.